This invention relates to a method and apparatus for controlling the sex of mammalian offspring by separation of X-chromosome female producing sperm of one density from Y-chromosome male producing sperm of a differing density.
As discussed in the aforementioned application, the sex of offspring is controlled by the chromosomes of the particular sperm cell which fertilizes the egg. As further disclosed therein, X-chromosome containing sperm which are responsible for producing female offspring are somewhat more dense than Y-chromosome containing sperm which are responsible for producing male offspring. This difference in density makes possible the separation of sperm into fractions containing substantially all of either the X or the Y sperm. Separation techniques utilizing this density differential are suitable for use with all mammals including human beings and other primates, cattle, swine, sheep, rabbits, cats, goats, horses, donkeys and buffalo. As previously disclosed, mainly in application Ser. No. 443,473, the method of separation has been to apply a buoyant force to the sperm to cause the more buoyant sperm to attain a different level in the separation medium than the less buoyant sperm, where the buoyant force applied has been either positive or negative.
It has been noted in the past that the presence of foreign particles in the medium disturbs the buoyant or sedimentation velocity of the sperm as well as the fertilization capacity after separation. The use of the universal medium disclosed in U.S. Pat. No. 3,816,249 substantially eliminates this problem and in addition promotes control of cellular hyperactivity and prolongs sperm life as well. The use of the universal medium as well as the imposition of a low temperature immobilizing the sperm prevents the small difference in density (2 to 5%) between male and female sperm from being neutralized by the high metabolic activity of the sperm.